Preliminary Exploration Of The Role Of HDAC In The Pathogenesis Of Idiopathic Interstitial Pneumonia

Background and Objective Cryptogenic organizing pneumonia(COP)and Idiopathic pulmonary fibrosis(IPF)are both belong to idiopathic interstitial pneumonias(IIPs).Fibroblasts and myofibroblasts can be seen in both of their pathologies.However,COP can be reversed by glucocorticoids whose prognosis is much better than IPF.The reason is still unknown.Histone acetylation and deacetylation modification can regulate the transcription of downstream genes by changing the affinity of histone and DNA.Recent studies indicated that histone deacetylase(HDAC)activity is also associated with the development and progression of organ fibrosis.And HDAC may affect the efficacy of glucocorticoid by affecting the balance of histone acetylation and deacetylation.Here,we investigate the expression of HDAC in peripheral blood and lung tissue from IPF and COP patients.We analyze the correlation between the HDAC overall activity of peripheral blood and some clinical parameters.Therefore,the current study was designed to evaluate the possible role of HDAC in the pathogenesis of IPF and COP.And our long-term goal is to develop a more efficacious therapeutic for IPF patients.Methods Fifteen IPF patients and Fifteen COP patients from Peking Union Medical College Hospital were recruited from March 2018 to October 2018.Fifteen healthy donors were enrolled as controls.Peripheral blood mononuclear cells(PBMC)were isolated and the nuclear and cytoplasmic protein were extracted by Nuclear Extraction Kit.HDAC activity was measured by fluorimetric method.The relations between HDAC activity and clinical parameters were analyzed with SPSS.Then,five IPF lung tissue,five COP lung tissue and five normal lung tissue which was at least 5cm away from the leision were collected.HE staining was carried out to locate the lung tissue with the most fibroblasts.We used real time-PCR and immunohistochemistry staining to evaluate the expression of class I HDAC in the lung tissue of each group.Furthermore,the mRNA expression of FAS,Thy-1 and GR 0 were detected to get more information.Results(1)The HDAC activity of cytoplasmic protein and nuclear protein from patients with IPF were(724±216)nmol/L and(2309±708)nmol/L,which were higher than that of health controls which were(409±105)nmol/L and(1572 ± 611)nmol/L(P<0.01 for both).So as to the HDAC activity of cytoplasmic protein and nuclear protein from patients with COP which were(718±245)nmol/L and(3310±1005)nmol/L(P<0.01 for both).The HD AC activity of nuclear protein from COP patients was higher than that from IPF patients(Z=-2.840,P=0.005).The HD AC activity of nuclear protein was negatively correlated with FEV1 and DLCO in IPF patients(r=-0.574,P=0.025;r=-0.583,P=0.029).The HDAC activity of nuclear protein was negatively correlated with FVC and TLC in COP patients(r=-0.846,P=0.016;r=-0.900,P=0.015).(2)There were some differences in the expression of class I HDAC gene between IPF and COP lung tissue.The expression of HDAC2 mRNA level of IPF patients was higher than that of COP and controls(P=0.044;P=0.018).While,the expression of HDAC3 mRNA level of IPF and COP were both lower than controls(P=0.043;P=0.001).There was no statistical difference in the expression of HDAC 1 and HDAC8 mRNA level in three groups(F=0.1153 P=0.892;x2=4.340,P=0.114).The expression of Thy-1 and FAS mRNA level of IPF and COP were both lower than those of controls(all P<0.05).However,there was no statistical difference between IPF and COP groups(P>0.05 for both).There was no statistical difference in the expression of GR ? mRNA level in three groups(F=3.243?P=0.075).Immunohistochemical staining showed that HDAC1 and HDAC2 were negative in fibroblasts from normal lungs.While,they were positive in fibroblasts from IPF and COP lungs.Furthermore,the expression of HDAC 1 in both COP fibroblasts and inflammatory cells were higher than that in IPF.The expression of HDAC2 in IPF fibroblasts were higher than that in COP,but lower in inflammatory cells(all P<0.05).Conclusion The overall HDAC activity of peripheral blood in IPF and COP patients were increased,and the expression of HDAC 1 and HDAC2 in their pulmonary fibroblasts were also up-regulated.The HDAC activity of PBMC nuclear protein may be related to the degree of pulmonary fibrosis.The up-regulation of HDAC1,2 in lung fibroblasts may be related to the down-regulation of its Thy-1 and FAS mRNA expression,which result in the abnormal accumulation of fibroblasts.There was no abnormal up-regulation of GR ? in IPF.The down-regulation of HDAC 1,2 in IPF inflammatory cells may partially explain its poor response to glucocorticoid.